Method and apparatus for resource locator identifier rewrite

ABSTRACT

A method for resource locator identifier rewrite in which a network security proxy insures that a resource locator identifier of a response indicates a resource access protocol that should govern a corresponding request. A security device receives from a resource host over a non-secure hypertext transfer protocol (HTTP) session a response to a request received from a client over a secure HTTP session. The response includes a uniform resource locator (URL) that is supposed to be for a resource host, but the URL does not designate a secure resource access protocol and the resource host requires the secure resource access protocol. The URL is located in the response and modified to designate the secure resource access protocol. After modification, the response is transmitted via the secure resource access protocol session to the client.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of communication. More specifically,the invention relates to communication networks.

2. Background of the Invention

Hypertext transfer protocol (HTTP) is a resource access protocol. Aresource access protocol is a defined set of rules for retrieval ofresources from the Internet. A resource can be an image, a hypertextmarkup language (HTML) page, a Java applet, program, etc. HTTP isconsidered to reside at the presentation layer and/or the applicationlayer of the OSI reference model. HTTP provides guidelines for exchangesbetween clients and resource hosts including request and responsemessages. A typical HTTP exchange includes a client requesting aresource and a resource host responding with the resource. In certainscenarios, the resource host will transmit a response that redirects theclient to a different resource than the one originally requested by theclient. For example, a resource host may not find a requesting client'scookie in the resource host's database, and, as a result, sends aresponse to the requesting client that redirects the client to a loginpage.

Since the exchanges between clients and resource hosts often includesensitive information, security measures are applied to certainexchanges. For security, HTTP is coupled with the Secure Sockets Layer(SSL) (also known as Transport Layer Security (TLS)). From theperspective of the OSI reference model, HTTP sits over SSL. Thiscoupling is referred to as HTTPS. After HTTP has generated a message,HTTP passes the message to SSL, which performs security operations(e.g., encryption, hashing, etc.) on the message.

HTTP uses a uniform resource locator (URL) for retrieval of a resource.A URL is an address of a resource accessible on the Internet. A URLincludes a resource access protocol identifier, a resource hostidentifier, a path identifier, and a resource identifier. In the URL“http://www.host.com/folder/main.html,” the resource access protocolidentifier is “http”; the resource host identifier is “www.host.com”;the path identifier is “folder”; and the resource identifier is“main.html.”

The resource access protocol identifies HTTP as the resource accessprotocol to be used to retrieve the identified resource.

The resource host indicated by the resource host identifier is aresource host, or server, identified as “www.host.com.” Although theresource host identifier used above is a domain name, a resource hostidentifier may be a network address, such as an Internet Protocol (IP)address. A resource host identifier may identify a port in addition to aresource host. For example, the following two URLs identify the sameresource, but the second indicates a port:

-   -   1) http://www.host.com/main.html    -   2) http://www.host.com:80/main.html.

The indicated port is the appropriate port for communication with theidentified resource host in accordance with the identified resourceaccess protocol. The default port for HTTP is port 80 (the default portfor HTTPS is port 443), so an HTTP message with the above example URLwill be communicated to the resource host identified as “www.host.com”with the port 80.

A URL does not necessarily have to include a path identifier or aresource identifier because the resource may be in a default path andhave a default name. Using the previous examples, the URL“http://www.host.com/” identifies the same resource as the previousexample URLs, assuming that “folder” is the default path and that“main.html” is the default resource.

The HTTP protocol and HTTPS protocol were designed such that theresponse (including a redirect) to a request will use the same protocolas the request used. Thus, if the request used HTTP, then the URLs ofthe response will use HTTP. In contrast, if the request used HTTPS, thenthe URLs of the response will use HTTPS. While this works for manysituations, it creates problems in certain environments.

FIG. 1 (Prior Art) is a diagram of an example redirect responseretransmission. In FIG. 1, a first, second, and third columns indicateresource messages respectively transmitted and received by a client 101,a content switch 103 that performs HTTP proxy, and a server 105. Ahyperlink with a URL “https://www.host.com/res1.htm” is activated at theclient 101, typically a personal computer. The resource host identifieris resolved to an Internet Protocol (IP) address and an HTTPS session isopened with the content switch 103. After the HTTPS session is opened, arequest message 107 with “GET res1.htm” is transmitted from the client101 to the content switch 103. The content switch 103 receives therequest 107 on port 443, decrypts the request 107, and forwards thedecrypted request 107 over an HTTP session to the server 105.

The content switch 103 that performs HTTP proxy and the server 105 aretypically network elements in the same local area network (LAN), whichis separate from the client 101. The client 101 communicates with theLAN over a public network (e.g., the Internet). The server 105 is one ofmany servers in a server farm. The server 105 and the other servers inthe server farm are not burdened with security measures since the ownerof the server farm and content switch 103 relies on the content switch103 for security. The content switch 103 is exposed to the outside worldand protects the server farm by performing HTTP proxy. The owner hasdedicated resources of the servers in the server farm, including theserver 105, to serving of requests instead of performing securityoperations. The content switch 103 performs HTTP proxy for the serversin the server farm and determines the appropriate server for a receivedrequest. In FIG. 1A, the server 105 is the appropriate server for therequest 107.

The server 105 transmits a response 111 with redirect URL“http://www.host.com/res2.htm” to the content switch 103. The contentswitch 103 encrypts the response 111 and transmits the encryptedresponse 111 back over the HTTPS session to the client 101. The client101 receives the HTTPS response 111, decrypts the response 111, andcloses the HTTPS session. Assuming the redirect URL is selected, theclient 101 resolves the host name and opens an HTTP session with thecontent switch 103 in accordance with the resource access protocolindicated by the redirect URL. The client 101 transmits a requestmessage 113 with “GET res2.htm” to the content switch 103.

The content switch 103 receives the request message 113 on the port 80because the content switch is running a network service to listen fortraffic received on port 80. Traffic received on port 80 is redirected.In response to the request 113, the content switch 103 generates aresponse message 119 that indicates a redirect URL“https://www.host.com/res2.htm”. The content switch 103 transmits theresponse 119 back to the client 101 over the HTTP session initiallyopened by the client 101.

The client 101 closes the HTTP session and opens a HTTPS session withthe content switch 103. The client 101 generates a request message 121,encrypts the request message 121, and transmits the encrypted requestmessage 121 to the content switch 103.

This redirect retransmission punches a hole in the security provided byHTTPS. Since the client switches to HTTP, the data transmitted from theclient is unencrypted. It is assumed that the client is transmittingsensitive information (e.g., a credit card number, passwords, bankaccount numbers, residential address, phone numbers, etc.) since HTTPSis typically invoked for protecting communications that will most likelyinclude sensitive information. Due to the redirect rewriteretransmission, the client is transmitting sensitive data withoutencryption, which can be captured and used with ease.

In addition, the number of exchanges taking place between the client 101and the content switch 103 illustrated in FIG. 1 are unnecessary “extra”exchanges to force the client to transmit an acceptable request, whichcan cause substantial impact to the content switch's performance in thereal world. These extra exchanges between a content switch and thousandsof sessions for thousands of clients impact performance of the contentswitch and introduce latency in a client's wait time for a response.Both the client machine and the content switch must process anadditional message per redirect. The additional redirect may alsoagitate users and deter them from returning to a website.

FIG. 2 (Prior Art) is an example of a client in a protected networkreceiving a response message with a URL that indicates HTTPS. In FIG. 2,four columns respectively indicate a client 201, an intrusion detectionsystem (IDS) 202, a firewall 203 with a proxy, and a server 205. Thefirewall 203 connects external networks to the client 201. The IDS 202sniffs traffic transmitted and received by the client 201. The server205 transmits a response 207 with a URL “https://www.host.com/res1.htm”to the firewall 203. The firewall 203 receives the response 207 andforwards the response 207 to the client 201 (assuming the client 201 wasthe requesting client). If the firewall 203 has a HTTPS session openwith the server 205, then the firewall 203 decrypts the response 207before forwarding it to the client 201. The IDS 202 analyzes theresponse 207. Assuming the URL in the response 207 is selected, theclient 201 resolves the host name of the URL and opens a HTTPS sessionwith the firewall 203 in accordance with the URL. If the client 151 doesnot support SSL (e.g., corporate entities that wish to snoop trafficwith an IDS, sometimes do not enable SSL on their client machines sothat their traffic can be snooped by the IDS), then the client 201cannot request the resource. The client 201 generates a request message209, encrypts the request 209, and transmits the request 209 to thefirewall 203. Since the request 209 is encrypted, the IDS 202 must becapable of decrypting the request 209 to analyze it, allow the requestto pass without analysis, or hold the request. If the IDS 202 allows therequest to pass, then the firewall 203 opens a HTTPS session with theserver 205 and transmits the request 209 to the server 205. Hence, therequest 209 has bypassed the IDS 202.

This security architecture is typically employed in a corporateenvironment. A corporate entity needs to protect its systems from beinginfected and/or prevent access to its systems by external and/orinternal malignant elements while still enabling its employees to accessresource beyond its local area network. The corporate entity also needsto control the types of resources or material that enters its network atthe request of its employees. Therefore, a corporate entity employs botha firewall with proxy support and an intrusion detection system toprotect its network from external hacking and internal violations of itscomputer use policy. Unfortunately, as shown in FIG. 2, an IDS can bebypassed with encryption.

Service provides also used another mechanism with a security flaw toaccommodate users. In order to avoid agitating users with error messagesand increasing latency, service providers allowed a pass through formessages that were not encrypted. For this mechanism, a content switchis configured to listen for traffic on both ports 80 and 443. Trafficreceived on port 80 is forwarded to the corresponding servers whiletraffic received on port 443 is decrypted. Hence, users are notinconvenienced with error messages and increased latency, but users werepossibly transmitting sensitive information without encryption.

BRIEF SUMMARY OF THE INVENTION

A method and apparatus for resource locator identifier rewrite isdescribed. According to one aspect of the invention, a method in anetwork security device provides for the receipt from a resource hostover a non-secure hypertext transfer protocol (HTTP) session a responseto a request received from a client over a secure HTTP session. Theresponse includes a uniform resource locator (URL) that is supposed tobe for a resource host, but the URL does not designate a secure resourceaccess protocol and the resource host requires the secure resourceaccess protocol. The URL is located in the response and is modified todesignate the secure resource access protocol. The response istransmitted via the secure resource access protocol session to theclient.

These and other aspects of the present invention will be betterdescribed with reference to the Detailed Description and theaccompanying Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 (Prior Art) is a diagram of an example redirect responseretransmission.

FIG. 2 (Prior Art) is an example of a client in a protected networkreceiving a response message with a URL that indicates HTTPS.

FIG. 3A is an exemplary flowchart for RLI rewrite according to oneembodiment of the invention.

FIG. 3B is an exemplary diagram of forward RLI rewrite for redirectaccording to one embodiment of the invention.

FIG. 3C is an exemplary diagram of reverse RLI rewrite according to oneembodiment of the invention.

FIG. 4A is an exemplary flowchart for processing a request for redirectresource locator identifier rewrite according to one embodiment of theinvention.

FIG. 4B is an exemplary flowchart for processing a resource response forredirect resource locator identifier rewrite according to one embodimentof the invention.

FIG. 5A is an exemplary flowchart for processing a request for generalresource locator identifier rewrite without persistent connectionaccording to one embodiment of the invention.

FIG. 5B is an exemplary flowchart for processing of a resource responsefor general resource locator identifier rewrite without persistentconnection according to one embodiment of the invention.

FIG. 6A is an exemplary flowchart for processing a resource request forgeneral resource locator identifier rewrite with persistent connectionaccording to one embodiment of the invention.

FIG. 6B is an exemplary flowchart for processing a resource response forgeneral resource locator identifier rewrite with persistent connectionaccording to one embodiment of the invention.

FIG. 6C is an exemplary flowchart continuing from FIG. 6B according toone embodiment of the invention.

FIG. 7A is an exemplary diagram illustrating processing of a request inone port mode for resource locator identifier rewrite according to oneembodiment of the invention.

FIG. 7B is an exemplary diagram illustrating processing of a response inone port mode for resource locator identifier rewrite according to oneembodiment of the invention.

FIG. 8A is an exemplary diagram illustrating processing of a request inin-line mode for resource locator identifier rewrite according to oneembodiment of the invention.

FIG. 8B is an exemplary diagram illustrating processing of a response inin-line mode for resource locator identifier rewrite according to oneembodiment of the invention.

FIG. 9A is an exemplary-flowchart for processing a request for reverseRLI rewrite according to one embodiment of the invention.

FIG. 9B is an exemplary flowchart for processing a response for reverseRLI rewrite according to one embodiment of the invention.

FIG. 10A is an exemplary diagram illustrating a reverse RLI rewritearchitecture sending a request according to one embodiment of theinvention.

FIG. 10B is an exemplary diagram illustrating a reverse RLI rewritearchitecture receiving a response according to one embodiment of theinvention.

FIG. 11A is a conceptual diagram illustrating exemplary processing of arequest with reference to layers from the OSI reference model accordingto one embodiment of the invention.

FIG. 11B is a conceptual diagram illustrating exemplary processing of aresponse with reference to layers from the OSI reference model accordingto one embodiment of the invention.

FIG. 12 is an exemplary conceptual diagram illustrating resource locatoridentifier rewrite with a ring buffer according to one embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous specific details are set forth toprovide a thorough understanding of the invention. However, it isunderstood that the invention may be practiced without these specificdetails. In other instances, well-known circuits, structures, standards,and techniques have not been shown in detail in order not to obscure theinvention.

Methods and apparatuses for resource locator identifier rewrite aredescribed. According to various embodiments of the invention, resourcelocator rewrite insures that the resource access protocol indicated bythe resource locator identifiers in a response, whether in the headerand/or embedded in the body of the response, is the resource accessprotocol that should govern a request for the resource located by thatresource locator identifier. Resource locator identifier (RLI) rewritecan be applied for both forward rewrite (non-secure to secure) andreverse rewrite (secure to non-secure). Furthermore, forward RLI rewritecan be applied for rewriting RLIs in the header of a message (e.g.,redirects) and/or for rewriting RLIs embedded in the body of a message.

FIGS. 3A-3C illustrate RLI rewrite for different applications. FIG. 2Aillustrates a generic RLI rewrite that can be applied regardless of thescenario. FIG. 2B illustrates RLI rewrite as applied to forward redirectrewrite and FIG. 2C illustrates RLI rewrite as applied to reverserewrite. Other scenarios, such as forward RLI rewrite with persistentconnection and forward RLI rewrite without persistent connections, aredescribed in later Figures.

FIG. 3A is an exemplary flowchart for RLI rewrite according to oneembodiment of the invention. At block 321, a response with at least oneRLI (e.g., a URL) is received. At block 323, a RLI is located andselected. At block 325, it is determined if the selected RLI indicates aresource access protocol desired to govern a request for the resourceidentified by the RLI. For example, assume the RLI is a URL thatindicates HTTP and a network device (e.g., a content switch, a securityoffloader, a security accelerator, a firewall, etc.) that performs RLIrewrite has been configured and/or programmed so that requests for theresource identified by the URL should be governed by HTTPS. The networkdevice will determine that the desired access protocol for the resourceis HTTPS. Likewise, if the URL indicates HTTPS and the network devicehas been configured and/or programmed so that requests for the resourceshould be governed by HTTP, then the network device will determine thatHTTP is the appropriate request governing resource access protocol. Ifit is determined that the RLI does not indicate the appropriate requestgoverning resource access protocol, then control flows to block 327. Ifit is determined that the RLI indicates the appropriate requestgoverning resource access protocol, then control flows to block 329.

At block 327, the response is transmitted.

At block 329, the response is modified to indicate the appropriaterequest governing resource access protocol. At block 331, it isdetermined if the response includes additional RLIs. If the responseincludes additional RLIs, then control flows back to block 333. If theresponse does not include additional RLIs, then control flows to block333.

At block 333, the modified response is transmitted. In one embodiment ofthe invention, modifications to the response only take place at thelayer of the resource access protocol (e.g., the RLI is rewritten only).In another embodiment of the invention, the modifications take place atthe layer of the resource access protocol and at lower layers, whichwill be described in more detail herein. Alternative embodiments mayperform the modification(s) in other layers.

FIG. 3B is an exemplary diagram of forward RLI rewrite for redirectaccording to one embodiment of the invention. In FIG. 3B, a client 301transmits resource request message 207 over a secure resource accessprotocol session (e.g., a HTTPS session) to a resource locatoridentifier (RLI) rewrite network security proxy 303. The RLI rewritenetwork security proxy 303 receives the request 307 on the secureresource access protocol session and decrypts the request 307. Afterdecrypting the request 307, the proxy 303 forwards the request 307 overa non-secure resource access protocol session to a resource host 305that is behind the RLI rewrite network security proxy 303. The resourcehost 305 transmits a response 311 having a RLI that indicates anon-secure resource access protocol back over the non-secure resourceaccess protocol session to the RLI rewrite network security proxy 303.The RLI rewrite network security proxy 303 recognizes that the RLI inthe response 311 should indicate a secure resource access protocol,which will be described in more detail later. The RLI rewrite networksecurity proxy 303 rewrites the RLI to indicate the secure resourceaccess protocol encrypts the response 311, and transmits the encryptedresponse 311 with the rewritten RLI back over the secure resource accessprotocol session to the client 301.

The client 301 requests the resource identified by the RLI in theresponse 311. A request 315 is generated and transmitted over the secureresource access protocol session to the RLI rewrite network securityproxy 303. Regardless of whether the RLI is a redirect or anon-redirect, the RLI rewrite network security proxy 303 does not bouncea response back to the client 301 to force the client 301 to switchsession types because the client 301 is requesting in accordance withthe appropriate request governing resource access protocol, due to theRLI rewrite performed by the RLI rewrite network security proxy 303 onthe response 311. The RLI rewrite network security proxy 303 decryptsthe request 315 and forwards the decrypted request message 315 to theresource host 305.

As can been seen from FIG. 3B, the client does not transmit a request tothe RLI rewrite network security proxy that is not encrypted. Hence,there no longer is a hole in the security provided by the secureresource access protocol. That is to say, the information exchangesbetween a client and a resource host remain secure if so desired.Maintaining information security prevents exposure of sensitiveinformation and protects the owners of that information. Furthermore,additional message exchanges between a client and a network securitydevice protecting a resource host are eliminated. The elimination of theoperations resulting from the additional message exchanges reducesresource consumption, improves performance of network security devicesinvolved in the message exchanges, and provides a less time consumingexperience for users requesting resources from resource hosts (i.e.,resource hosts located behind network security devices). In addition,resource hosts remain secure behind network security devices withoutmodifying applications on resource hosts and increasing their burdens.

The RLI rewrite technique illustrated in FIG. 3A can also be applied forreverse RLI rewrite, which is described with reference to FIG. 3C.

FIG. 3C is an exemplary diagram of reverse RLI rewrite according to oneembodiment of the invention. In FIG. 3C, four columns respectivelyindicate a client 341, an IDS 342, a RLI rewrite network security proxy343, and a resource host 345. The client 341 transmits a request message351 over a non-secure resource access protocol session establishedbetween the client 341 and the proxy 343. An IDS 342 between sniffsdata, including the request 351, transmitted from the client 341 to theproxy 343. The proxy 343 receives the request 351 on the non-secureresource access protocol session, encrypts the request 351, andtransmits the request over a secure resource access protocol session tothe resource host 345.

The resource host 345 generates a response message 355 that has a RLIthat indicates a secure resource access protocol. The resource hosttransmits the response 355 over the secure resource access protocolsession to the proxy 343. The proxy 343 receives the response 355 on thesecure resource access protocol session, decrypts the response 355, andrecognizes that the response 355 indicates a secure resource accessprotocol, which is not the appropriate request governing resource accessprotocol from the perspective of the proxy 343. Therefore, the proxy 343rewrites the RLI to indicate a non-secure resource access protocol andforwards the decrypted response 355 with the rewritten RLI to the client341. Since the response 355 is decrypted, the IDS 342 can analyze theresponse 355 without having to support decryption.

As can be seen in FIG. 3C, RLI rewrite prevents resource messages (bothrequests and responses) from bypassing security devices, such as anintrusion detection system, and transmitting responses with RLIs that aclient cannot request because the client does not support the indicatedresource access protocol.

Forward RLI Rewrite

As previously stated, RLI rewrite can be applied for RLIs in the headerof a message, such as for redirect, and/or for RLIs in the body.

Header Forward RLI Rewrite

FIGS. 4A-4B are exemplary flowcharts for redirect resource locatoridentifier rewrite according to one embodiment of the invention. FIG. 4Ais an exemplary flowchart for processing a request for redirect resourcelocator identifier rewrite according to one embodiment of the invention.At block 403, a resource request message from a client is received overa secure resource access protocol session. At block 405, the request isdecrypted. At block 407, the decrypted request is forwarded to theappropriate resource host over a non-secure resource access protocolsession.

FIG. 4B is an exemplary flowchart for processing a resource response forredirect resource locator identifier rewrite according to one embodimentof the invention. At block 411, a resource response is received from theresource host. At block 413, it is determined if the resource responseis a redirect. For example, a HTTP response is a redirect response ifthe status in the header of the HTTP response begins with the number 3.A RLI rewrite network security proxy will scan the header of theresponse for the status field and determine if the status value is 3xx.If it is determined that the resource response is not a redirect, thencontrol flows to block 423. If it is determined that the resourceresponse is a redirect, then control flows to block 415.

At block 423, the resource response is processed (e.g., the response isencrypted, encapsulated, transmitted, etc.).

At block 415, a URL of the redirect resource response is rewritten. Atblock 417, the resource response is encrypted. At block 421, theresource response is transmitted to the requesting client over thesecure resource access protocol session.

General Forward RLI Rewrite

The Header Forward RLI rewrite describes rewriting RLIs in the header ofa message, but does not describe rewriting RLIs in the body of amessage. The general forward RLI rewrite described in the followingfigures can be applied to rewrite RLIs in the body or in the header andbody of a message. RLI rewrites made to the body of a message arerelatively more complicated than RLI rewrites made to the header of amessage because considerations are made for changing the size of thecontent in the body of a message. Various embodiments of the inventionperform RLI rewrites to the body of a message differently, but twoembodiments are described below. In one embodiment of the invention,general forward RLI rewrite is performed without persistent connection.In another embodiment of the invention, general forward RLI rewrite isperformed with persistent connection. Although these two embodiments ofthe invention are illustrated with forward RLI rewrite, reverse RLIrewrite can also be performed with persistent connection and withoutpersistent connection.

General Forward RLI Rewrite Without Persistent Connections

FIGS. 5A-5B are exemplary flowcharts for general resource locatoridentifier rewrite without persistent connections according to oneembodiment of the invention. FIG. 5A is an exemplary flowchart forprocessing a request for general resource locator identifier rewritewithout persistent connection according to one embodiment of theinvention. At block 501, a resource request message is received over asecure resource access protocol session. At block 503, the request isdecrypted. At block 505, the type of transfer encoding indicated assupported by the requesting client is determined from the resourcerequest message. If the request indicates that non-chunked transferencoding is supported by the client, then control flows to block 509. Ifthe resource request indicates that chunked transfer encoding issupported by the client, then control flows to block 507.

At block 507, it is ensured that the resource request does not indicatethat chunked transfer encoding is supported (e.g., if the resourcerequest is a HTTP request, then downgrading the version indicated in therequest from 1.1 to 1.0). At block 509, it is ensured that the requestdoes not indicate that persistent connection is supported. Again usingHTTP as an example, indicating that persistent connection is notsupported can be done by modifying the connection parameter in theheader of the HTTP request from “Keep-Alive” to “close<5 spaces>” orappending “Connection: close” to the header. At block 513, the requestis communicated to a resource host over a non-secure resource accessprotocol session.

FIG. 5B is an exemplary flowchart for processing of a resource responsefor general resource locator identifier rewrite without persistentconnection according to one embodiment of the invention. At block 515, aresponse is received. At block 517, it is determined if the content typeof the resource response is text. If the content type is text, thencontrol flows to block 521. If the content type is not text (e.g.,image, audio, multipart HTTP responses, etc.), then control flows toblock 519. Skipping processing of responses with non-text content typeincreases efficiency and performance.

At block 519, the response is communicated to the requesting client overthe secure resource access protocol session.

At block 521, the type of transfer encoding indicated as supported bythe resource host is determined from the response. If the responseindicates that non-chunked transfer encoding is supported, then controlflows to block 525. If the resource response indicates that chunkedtransfer encoding is supported, then control flows to block 523.

At block 523, it is ensured that the response does not indicate thatchunked transfer encoding is supported. At block 525, it is ensured thatthe response does not indicate that persistent connection is supported.At block 526, a content length field is effectively removed from theresponse. For example, if the resource request is a HTTP request thenthe header parameter “Content-Length: xxx” is modified to“Content_Length: xxx.” As shown in the above example, the content lengthfield “Content-Length: xxx” is effectively removed by replacing thehyphen in the label of the field with an underscore such that a clientreceiving the response is unable to recognize the content length field.As a result, the client is prevented from using the content lengthindicated in the response. At block 527, the response is scanned forRLIs that do not indicate an appropriate request governing resourceaccess protocol, and those URLs are rewritten to indicate theappropriate request governing resource access protocol. For example,assume a RLI rewrite network security proxy, which is protectingresource hosts, has a rewrite configuration file with the followingentries:

-   -   www.securehost.com    -   www.resourcehost.com    -   9.120.*.*        If the RLI rewrite network security proxy finds a RLI that        identifies a resource host that matches one of the resource        hosts in the rewrite configuration file and that does not        indicate a secure resource access protocol (assuming the        appropriate request governing resource access protocol is a        secure resource access protocol), then the RLI rewrite network        security proxy will rewrite that RLI to indicate the secure        resource access protocol. Although the example assumes the        alternative to the appropriate request governing resource access        protocol is a non-secure resource access protocol, in        alternative embodiments of the invention the appropriate request        governing resource access protocol is a particular secure        resource access protocol. In such an embodiment, a RLI may        indicate a secure resource access protocol, but be rewritten        because it is not the particular secure resource access protocol        that is desired. In such an embodiment, the appropriate request        governing resource access protocol is defined in the        configuration file and not assumed as in the above example that        does not indicate any resource access protocol and relies on a        default appropriate request governing resource access protocol.

Control flows from block 527 to block 519.

Since the size of a response will probably change due to resourcelocator identifier rewrite, the size of the response will be incorrectunless recomputed by the resources access protocol match assurance proxyor the client. Modifying messages to indicate that persistent connectionis not supported (or disabled) and causing the header field“Content-Length” to effectively disappear forces the client to rely onclose of the session to compute the length of the response it receives.

General Forward RLI Rewrite With Persistent Connection

FIGS. 6A-6C are exemplary flowcharts for general resource locatoridentifier rewrite with persistent connection according to oneembodiment of the invention. FIG. 6A is an exemplary flowchart forprocessing a resource request for general resource locator identifierrewrite with persistent connection according to one embodiment of theinvention. At block 601, a resource request message is received over asecure resource access protocol session. At block 602, the request isdecrypted. At block 603, the type of transfer encoding indicated assupported by the client is determined from the resource request message.If the resource request indicates support of non-chunked transferencoding, then control flows to block 605. If the resource requestindicates support of chunked transfer encoding, then control flows block607.

At block 607, it is ensured that the request does not indicate thatchunked transfer encoding is supported. At block 609, the boundaries ofthe request are parsed. Control flows from block 609 to block 610.

At block 605, it is ensured that the request does not indicate thatpersistent connection is supported. At block 610, the type of transferencoding indicated as supported by the requesting client is stored. Atblock 611, the request is communicated to the appropriate resource hostover a non-secure resource access protocol session.

FIG. 6B is an exemplary flowchart for processing a resource response forgeneral resource locator identifier rewrite with persistent connectionaccording to one embodiment of the invention. At block 613, a responseis received. At block 614, it is determined if the content type of theresource response is text. If the content type of the resource responseis text, then control flows to block 615. If the content type of theresource response is not text, then control flows to block 616 of FIG.6C.

At block 615, it is determined if the response indicates a contentencoding. If the response does indicate a content encoding, then controlflows to block 616 of FIG. 6C. If the response does not indicate acontent encoding, then control flows to block 621.

At block 621, the type of transfer encoding supported by the client isdetermined. This information was previously stored at block 610 of FIG.6A. If the client supports chunked transfer encoding, then control flowsto block 622. If the client supports non-chunked transfer encoding, thencontrol flows to block 631.

At block 622, it is ensured that header of the response complies withchunked transfer encoding. At block 623, it is ensured that the body ofthe response complies with chunked transfer encoding. Control flows fromblock 623 to block 624 of FIG. 6C.

At block 631, the type of transfer encoding supported by the resourcehost is determined from the response. If the resource host supportschunked transfer encoding, then control flows to block 632. If theresource host supports non-chunked transfer encoding then control flowsto block 633.

At block 632, it is ensured that the response does not indicate thatchunked transfer encoding is supported. At block 633, it is ensured thatthe response does not indicate that persistent connection is supported.Control flows from block 633 to block 624 of FIG. 6C.

FIG. 6C is an exemplary flowchart continuing from FIG. 6B according toone embodiment of the invention. At block 616, the type of transferencoding indicated as supported by the client is determined. If theclient supports chunked transfer encoding, then control flows to block617. If the client supports non-chunked transfer encoding, then controlflows to block 618.

At block 617, the boundaries of the response are parsed. At block 618,the response is communicated to the requesting client over a secureresource access protocol session.

At block 624, the content length is effectively removed from theresponse. At block 625, the response is scanned for RLIs that do notindicate an appropriate governing resource access protocol for thatparticular RLI, and those RLIs are rewritten. Control flows from block625 to block 616.

Not disabling persistent connection as described in FIGS. 6A-6C allowsthe client to utilize chunked transfer encoding for requests whileavoiding receiving chunked transfer encoded responses from the resourcehost. The client and the RLI rewrite network security proxy can takeadvantage of the features of persistent connection without encounteringproblems of erroneous length values in the header of responses.

Header forward resource locator identifier rewrite and general forwardresource locator identifier rewrite can be implemented independently, incombination, etc. An entity may only wish to employ resource locatoridentifier rewrite for redirect scenarios. Another entity may wish toemploy resource locator identifier rewrite for all scenarios. Withgeneral forward resource locator identifier rewrite, the option is alsoavailable to maintain persistent connection features provided by HTTP1.1. Furthermore, the owner of a network security device may wish toemploy general forward resource locator identifier rewrite for allscenarios, or header forward resource locator identifier rewrite forredirect scenarios and general forward resource locator identifierrewrite for non-redirect scenarios.

Exemplary Forward RLI Rewrite Architectures

Various architectures can be used to implement forward RLI rewrite (beit redirect and/or general; be it persistent or non-persistent). By wayof illustrations, two such architecture are described below. While twosuch architectures are described, it should be understood that theinvention is not limited to these two exemplary architectures.

FIGS. 7A-7B are diagrams illustrating an exemplary one port modearchitecture according to one embodiment of the invention. FIG. 7A is anexemplary diagram illustrating processing of a request in one port modefor resource locator identifier rewrite according to one embodiment ofthe invention. In FIG. 7A, a content switch 703 receives an encryptedrequest 711 from a network cloud 721. The encrypted request 711 may havebeen transmitted directly from a requesting client, from an intermediarynetwork security device protecting the actual requesting client, etc.The content switch 703 resolves the encrypted request 711 to a rule thatindicates secure messages should be passed to a RLI rewrite networksecurity proxy 701. The proxy 701 decrypts the request 711 and forwardsthe decrypted request 711 back to the content switch 703. The contentswitch 703 then forwards the decrypted request 711 to the appropriateresource host within a server farm 705.

FIG. 7B is an exemplary diagram illustrating processing of a response inone port mode for resource locator identifier rewrite according to oneembodiment of the invention. In FIG. 7B, the appropriate resource hostwithin the server farm 705 transmits to the content switch 703 aresponse 707 having a RLI that indicates a non-secure resource accessprotocol. The content switch 703 passes the response 707 to the proxy701. The proxy 701 rewrites the RLI to indicate a secure resource accessprotocol and encrypts the response 707. The proxy 701 forwards theencrypted response 707 with the rewritten RLI to the content switch 703.The content switch 703 transmits the response 707 through the networkcloud 721 to the requesting client.

FIGS. 8A-8B are diagrams illustrating an exemplary in-line modearchitecture according to one embodiment of the invention. FIG. 8A is anexemplary diagram illustrating processing of a request in in-line modefor resource locator identifier rewrite according to one embodiment ofthe invention. In FIG. 8A, a RLI rewrite network security proxy 801receives an encrypted request 811 from a network cloud 821. As in FIG.7A, the encrypted request 811 may have been transmitted directly from arequesting client, from an intermediary network security deviceprotecting the requesting client, etc. The proxy 801 decrypts therequest 811 and forwards the decrypted request 811 to a content switch803. The content switch 803 determines the appropriate resource hostwithin a server farm 805 and transmits the decrypted request 811 to thatresource host.

FIG. 8B is an exemplary diagram illustrating processing of a response inin-line mode for resource locator identifier rewrite according to oneembodiment of the invention. In FIG. 8B, the appropriate resource hostwithin the server farm 805 transmits to the content switch 803 aresponse 807 having a RLI that indicates a non-secure resource accessprotocol. The content switch 803 passes the response 807 to the proxy801. The proxy 801 rewrites the RLI in the response 807 to indicate asecure resource access protocol and encrypts the response 807. The proxy801 transmits the encrypted response 807 with the rewritten RLI to therequesting client via the network cloud 821.

While two exemplary architectures have been described, it is understoodthat other architectures are within the scope of the invention.

Reverse RLI Rewrite

As with forward RLI rewrite, reverse RLI rewrite can be performed onRLIs in the header of a message and/or in the body of a message.

Header Reverse RLI Rewrite

Performing header reverse RLI rewrite is similar to performing headerforward RLI rewrite as described in FIGS. 4A-4B. FIGS. 9A-9B areexemplary flowcharts for performing header reverse RLI rewrite accordingto one embodiment of the invention.

FIG. 9A is an exemplary flowchart for processing a request for reverseRLI rewrite according to one embodiment of the invention. At block 901,a resource request message is received via a non-secure resource accessprotocol session. At block 903, the request is encrypted. At block 905,the request is communicated to a resource host via a secure resourceaccess protocol session.

FIG. 9B is an exemplary flowchart for processing a response for reverseRLI rewrite according to one embodiment of the invention. At block 909,a resource response message is received over a secure resource accessprotocol session. At block 911, the response is decrypted. At block 913,the response is scanned for RLIs that indicate a secure resource accessprotocol session and those RLIs are rewritten to indicate a non-secureresource access protocol. At block 915, the response (or fragments ofthe response) is encapsulated with the appropriate information. At block917, the decrypted response is communicated to the requesting clientover a non-secure resource access protocol session.

General Reverse RLI Rewrite

When performing reverse RLI rewrite on the body of a message, reverseRLI rewrite can be performed without persistent connection or withpersistent connection, similar to forward RLI rewrite as described abovein FIGS. 5A-5B and FIGS. 6A-6B. For general reverse RLI rewrite, atblock 501 of FIG. 5A and block 601 of FIG. 6A, the secure resourceaccess protocol session would be a non-secure resource access protocolsession and at block 513 of FIG. 5A and block 611 of FIG. 6A, thenon-secure resource access protocol session would be a secure resourceaccess protocol session. In addition, when the request is communicatedto the resource host as described in block 513 of FIG. 5A and block 611of FIG. 6A, the request would be encrypted instead of decrypted. InFIGS. 5B and 6B, the response would be decrypted for general reverse RLIrewrite after blocks 515 and 613. At block 519 of FIG. 5B and block 618of FIG. 6B, the decrypted resource response would be transmitted over anon-secure resource access protocol session to the requesting client forgeneral reverse RLI rewrite instead of a secure resource access protocolsession.

As previously stated with respect to forward RLI rewrite, header reverseresource locator identifier rewrite and general reverse resource locatoridentifier rewrite can be implemented independently, in combination,etc. An entity may only wish to employ resource locator identifierrewrite for redirect scenarios. Another entity may wish to employresource locator identifier rewrite for all scenarios. With generalreverse resource locator identifier rewrite, the option is alsoavailable to maintain persistent connection features provided by HTTP1.1. Furthermore, the owner of a network security device may wish toemploy general reverse resource locator identifier rewrite for allscenarios, or header reverse resource locator identifier rewrite forredirect scenarios and general resource reverse locator identifierrewrite for non-redirect scenarios.

Exemplary Reverse RLI Rewrite Architecture

FIGS. 10A-10B are diagrams illustrating an exemplary reverse RLI rewritearchitecture according to one embodiment of the invention. FIG. 10A isan exemplary diagram illustrating a reverse RLI rewrite architecturesending a request according to one embodiment of the invention. In FIG.10A, a client 1019 is protected by an intrusion detection system (IDS)1013 and a RLI rewrite network security proxy 1005. The client 1019 iscoupled with the IDS 1013. The IDS 1013 is coupled with the proxy 1005.A non-secure resource access protocol session 1009 is establishedbetween the client 1019 and the proxy 1005. The proxy 1005 hasestablished a secure resource access protocol session 1007 with anexternal network element (e.g., a resource host in a different localarea network) via a network cloud 1001.

The client 1019 transmits a request 1011 to the proxy 1005. As therequest passes through the IDS 1013, the IDS 1013 analyzes the request.In an alternative embodiment of the invention, data does not passthrough an IDS, but a security network device, such as an IDS, sniffsthe line between the client 1019 and the proxy 1005. The proxy 1005encrypts the request 1011 and transmits it to the network cloud 1001.

FIG. 10B is an exemplary diagram illustrating a reverse RLI rewritearchitecture receiving a response according to one embodiment of theinvention. The proxy 1005 receives an encrypted response 1003 that has aRLI indicating a secure resource access protocol. The proxy 1005decrypts the response 1003 and rewrites the RLI in the response 1003 toindicate a non-secure resource access protocol. The proxy 1005 forwardsthe decrypted response 1011 with the rewritten RLI to the client 1019through the IDS 1013. The IDS 1013 can analyze the response 1011 sinceit is decrypted. Since the RLI does not indicate a secure resourceaccess protocol, a request for the resource of that RLI from the client1019 will not be encrypted and can be sniffed or analyzed by the IDS1013.

Reverse resource locator identifier rewrite enables message exchangewithout bypassing security measures or hindering network securitydevices with support of encryption operations, such as an intrusiondetection system. In the example illustrated in FIGS. 10A-10B, theintrusion detection system 1013 can continue to analyze data transmittedbetween the client 1019 and the proxy 1005 without being saddled withdecryption duties since they are performed by the proxy 1005.

Combination of Forward and Reverse RLI Rewrite

It should be understood that both forward and reverse RLI rewrite can beimplemented separately or in various combinations. A RLI rewrite networksecurity proxy that performs forward RLI rewrite can communicate with aclient, a network security device that does not perform RLI rewrite, anetwork security device that performs reverse RLI rewrite, etc. A RLIrewrite network security proxy that performs reverse RLI rewrite cancommunicate with a network security device that does not perform RLIrewrite, a network security device that performs forward RLI rewrite, aresource host, etc. The benefits provided separately by forward andreverse RLI rewrite can all be realized in a scenario where a RLIrewrite network security proxy that performs forward RLI rewriteexchanges messages with a RLI rewrite network security proxy thatperforms reverse RLI rewrite.

Moreover, a local area network may include clients and resource hosts.In such a scenario, forward and reverse RLI rewrite can be respectivelyperformed in the LAN by separate intermediary network security devices;alternatively, a single intermediary network security device can performboth forward and reverse RLI rewrite. In one scenario, a RLI rewritenetwork security proxy that performs both forward and reverse RLIrewrite exchanges messages with another RLI rewrite network securityproxy that also performs both forward and reverse RLI rewrite.

Exemplary Processing of Resource Messages

The RLI rewrite network security proxies illustrated in the Figuresabove include memories, processors, and/or ASICs. Such memories includea machine-readable medium on which is stored a set of instructions(i.e., software) embodying any one, or all, of the methodologiesdescribed herein. Software can reside, completely or at least partially,within this memory and/or within the processor and/or ASICs. For thepurpose of this specification, the term “machine-readable medium” shallbe taken to include any mechanism that provides (i.e., stores and/ortransmits) information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes read onlymemory (“ROM”), random access memory (“RAM”), magnetic disk storagemedia, optical storage media, flash memory devices, etc., and acommunication medium includes electrical, optical, acoustical, or otherform of propagated signals (e.g., carrier waves, infrared signals,digital signals, etc.), etc.

FIGS. 11A-11B are conceptual diagrams illustrating exemplary processingof a resource message with reference to layers from the OSI referencemodel according to one embodiment of the invention. The processingillustrated in FIGS. 11A-11B is an example of the message processingperformed for any RLI rewrite (i.e., reverse RLI rewrite, generalforward RLI rewrite, redirect forward RLI rewrite, etc.). FIG. 11A is aconceptual diagram illustrating exemplary processing of a request withreference to layers from the OSI reference model according to oneembodiment of the invention. In FIGS. 11A-11B, only certain layers fromthe OSI reference model are illustrated in a multilayer block 1101. Theblock 1101 includes, from bottom to top, the network layer, thetransport layer, and the application/presentation layer. A request 1103is illustrated next to the application/presentation layer.

As the request 1103 is successively processed down the model at eachlayer, the request 1103 is modified and/or information is added and/orremoved from the request 1103. At the application/presentation layer,the request 1103 indicates a URL “http://www.host.com/res.htm.” Afterthe application/presentation layer, the resource access protocolidentifier and the resource host identifier are stripped out of therequest and the request is encrypted if the request is being transmittedover a secure resource access protocol session. At the transport layer,the request 1103 may be broken into fragments, but probably will not besince requests are typically small. At the transport layer, the strippedout resource access protocol identifier is used for the TCPencapsulation information 1105 that is added to the request 1103.

At the network layer, Internet Protocol (IP) encapsulation information1107 is added to an IP packet payload 1109, which is the TCPencapsulation information 1105 and the request 1103. The IP packetpayload 1109 with the IP encapsulation information 1107 is an IP packet1111. The IP encapsulation information 1107 is based on the stripped outresource host identifier. Operations for resource locator identifierrewrite take place at the application/presentation layer when modifyinga resource message and at the transport layer when modifying transportlayer information (e.g., TCP encapsulation information) to comply withmodifications made at the application/presentation layer.

FIG. 11B is a conceptual diagram illustrating exemplary processing of aresponse with reference to layers from the OSI reference model accordingto one embodiment of the invention. A response 1123 is illustrated nextto the application/presentation layer. As the response 1123 issuccessively processed down the model at each layer, the response 1123is modified and/or information is added and/or removed from the response1123. Any rewrite is performed at the application/presentation layer.Rewrites performed to RLIs may not indicate a port and rely on a defaultport for the indicated resource access protocol or a port defined forthe indicated resource host. For example, assume a RLI rewrite networksecurity proxy has a configuration file with the following entries:

www.host1.com port 443 www.host2.com port 999

When a RLI rewrite network security proxy rewrites a RLT that haswww.host1.com as the resource host identifier, it can either notindicate the port because the receiving client will use the defaultHTTPS port 443, or rewrite the resource host identifier aswww.host1.com:443. For rewrites of RLIs having www.host2.com as theresource host identifier, the RLI rewrite network security proxy willinclude the port 999 in the resource host identifier of the rewrittenURL (i.e., www.host2.com:999). In FIG. 11B, the response 1123 indicatesHTTP but the configuration file indicates that requests forwww.host1.com should be governed by HTTPS. Therefore, the RLI rewriteproxy will rewrite the RLI to “https://www.host1.com/res.htm.” Afterperforming rewrite the response 1123 will be encrypted if appropriate.

At the transport layer, the response 1123 may be broken into fragments.A response fragment 1126 is encapsulated with TCP encapsulationinformation 1125 in accordance with the resource access protocol sessionthat the response will be transmitted over.

At the network layer, Internet Protocol (IP) encapsulation information1127 is added to an IP packet payload, which is the TCP encapsulationinformation 1125 and the response fragment 1126. The IP packet payload1129 with the IP encapsulation information 1127 is an IP packet 1131.

FIG. 12 is an exemplary conceptual diagram illustrating resource locatoridentifier rewrite with a ring buffer according to one embodiment of theinvention. In FIG. 12, a resource access protocol module 1203 receivesresource messages 1211 over resource access protocol sessions. Theresource access protocol module 1203 includes a buffer daemon 1207 and ascan and parse daemon 1209. The buffer daemon 1207 loads message datainto a ring buffer 1201 and manages allocation and recycling of buffersfor the ring buffer 1201. Message data may be an entire message or partof a message.

In FIG. 12, the buffer daemon 1207 is illustrated as loading messagedata 1211 for a session A into a buffer 1202 of the ring buffer 1201,and loading message data 1213 for a session B into a buffer 1204 of thering buffer 1201. The individual buffers in a ring buffer can be definedwith any size. In the ring buffer 1201, each individual buffer isdefined with the same fixed size, although alternative embodiments ofthe invention provide for varying size buffers. In another embodiment ofthe invention, one ring buffer is allocated for resource requests and asecond ring buffer is allocated for resource responses.

Numerous factors should be considered when defining the size ofindividual buffers. Since resource request messages are typically small,each buffer is defined with the capacity for at least a single resourcerequest in one embodiment of the invention. In contrast, the typicallyvarying sizes of larger responses may require multiple buffers. In theembodiment of the invention illustrated in FIG. 12, a session is limitedto a single buffer within the ring buffer 1201. In other words, if themessage data 1211 is not an entire message and fills the buffer 1202,then the remainder of the message data will not be loaded into thebuffer 1202 or any other buffer until the message data 1211 in thebuffer 1202 has been scanned, parsed, analyzed, and flushed.

In one embodiment of the invention chunk creation is related to the ringbuffers while in another embodiment of the invention chunks are createdin relation to each processed RLI. In an embodiment that relates chunkcreation to the ring buffers, a chunk is created for each full set ofmessage data from a buffer in the ring buffer. If a buffer holds 2complete RLIs and 1 partial RLI, then a chunk will be created for all ofthe message data in the buffer including the 2 complete RLIs up to thepartial RLI. The buffer will be flushed after processing up to thepartial RLI, message data from the same message will be loaded into thebuffer in addition to the partial RLI, and the next chunk will becreated from all of the complete RLIs (including the RLI that waspreviously partial since it should be complete with newly loaded messagedata) after the message data in the buffer is processed.

The scan and parse daemon 1209 is illustrated in FIG. 12 as performingoperations 1215. The operations 1215 include scan, parse, and flushoperations. These operations are performed when certain items are beinglocated in a message (e.g., header parameters, RLIs, etc.). Inalternative embodiments of the invention the buffer daemon 1207 performsall loading and flush operations to the ring buffer 1201. In suchembodiments of the invention, flags are utilized for the scan and parsedaemon 1209 to communicate completion of operations on a buffer to thebuffer daemon. In another embodiment of the invention, the resourceaccess protocol module 1203 performs all of the operations withoutdaemons. In another embodiment of the invention, the resource accessprotocol module 1203 utilizes a single daemon to perform all theoperations on message data in the ring buffer 1201.

At some point before the scan and parse daemon 1209 begins to operate onthe message data 1211 for Session A in the buffer 1202 and/or themessage data 1213 for Session B in the buffer 1204, variables areinitialized. An instance of the variables shown in Table 1 below isinitialized for the message data 1211 and another instance for themessage data 1213.

TABLE 1 Variables for Processing Message Data Variable Example ValuesScan-and-Parse State URL Scan, Version Scan, Header Scan, Parse,Complete Connection Search State Boolean Content-Length Search StateBoolean Content-Length Data Size Kilobytes Transfer-Encoding SearchState Boolean Transfer-Encoding Data State Kilobytes PersistentConnection Disabled Boolean Message Type Response or RequestAlthough in one embodiment of the invention, an administrator staticallydefines the “Persistent Connection Disabled” variable, in alternativeembodiments of the invention this variable varies dynamically dependingon the session. The variables in the table above are initialized asshown in table 2 below.

TABLE 2 Initialization of Variables Variable Initialization Scan-and- IFMessage Type = Response AND Persistent Parse Connection Disabled = FalseTHEN SET TO State Header Scan ELSE SET TO Version Scan Connection IFPersistent Connection Disabled = Search True THEN SET TO TRUE StateContent- IF Message Type = Request AND Persistent Length ConnectionDisabled = TRUE OR Message Type = Search Response AND PersistentConnection Disabled = State False THEN SET TO TRUE ELSE SET TO FALSEContent- 0 Length Data Size Transfer- IF Message Type = Response ANDPersistent Encoding Connection Disabled = False THEN SET TO Search TRUEELSE SE TO FALSE State Transfer- 0 Encoding Data State Message TypeBased on Message

The scan and parse daemon performs the following sequence of operationsshown in Table 3 below depending on the values of the previouslydiscussed variables on each buffer with message data.

TABLE 3 Sequence of Scan and Parse Operations on Message DataControlling Operations Variables 1 SEARCH_FOR_VERSION → Scan-and- SETScan-and-Parse State Parse State TO Header Search when complete IFMessage Type = Response ELSE SET Scan-and- Parse State TO Parse 2SEARCH_FOR_HEADER→ Scan-and- SET Scan-and-Parse Parse State State TO URLScan 3 SEARCH_HEADER_(—) Connection CONNECTION Search State 4SEARCH_HEADER_(—) Content-Length CONTENT_LENGTH Search State 5PARSE_COMPUTE_(—) Content-Length CONTENT_LENGTH Search State 6SEARCH_HEADER_(—) Transfer- TRANSFER_ENCODING Encoding Search State 7PARSE_BODY_BASED_(—) Transfer- ON_CONTENT_LENGTH Encoding Search State 8PARSE_BODY_BASED_(—) Transfer- ON_TRANSFER_ENCODING Encoding SearchState

Table 4 below illustrates the relationships between the operationsillustrated in Table 4 by row number, the operations illustrated in theflowcharts of FIGS. 5A-5B and 6A-6B, and the exemplary processes thatperform the operations according to one embodiment of the invention.

TABLE 4 Relationships between Operations Scan and parse daemon ResourceAccess Protocol Module 1 Downgrade Version (Blocks 507, 523 and 607) 2Search for RLI that does not indicate appropriate request governingresource access protocol in Header and Rewrite (Block 415) 3 ModifyConnection Parameter (Blocks 509 and 525) 4 Use to Skip Body if Messageis Redirect Response Modify Parameter (Block 511) 5 Used for HeaderRewrite 6 Use to Skip Body if Message is Redirect Response Use to writeover Content-Length parameter (Block 511) 7 Used to parse boundaries ofmessages (Blocks 609 and 624) Used to convert content-length content tochunked transfer encoding content (Block 621) 8 Used to parse boundariesof messages (Blocks 609 and 624) Used to convert content-length contentto chunked transfer encoding content (Block 623)

Table 5 below illustrates the sequence of operations, identified by rownumber from Table 3 that will be performed on the different types ofmessage data.

TABLE 5 Sequence of operations for different message data PersistentConnection Disabled Persistent Connection Not Disabled Request ResponseRequest Response 1 1 1 2 2 2 5 4 3 3 7 5 4 6 7 8

The variables persist for a given message as long as the entire messagehas not been processed. For example, the instance of the variables forthe message data 1211 will persist until the entire messagecorresponding to the message data 1211 has been completely processed. Inone embodiment of the invention, once the entire message has beenprocessed, the buffer 1202 is returned to a memory pool.

In alternative embodiments of the invention, a temporary buffer isallocated for processed message data. For example, addition data (e.g.,header data) may need to be inserted into message data. Once the datathat should be before the header data has been scanned and processed, itis loaded from the ring buffer into an allocated temporary buffer. Theheader data is inserted and/or space is reserved for additional data inthe temporary buffer. After the insertion and/or reservation, the restof the message data from the ring buffer is loaded into the temporarybuffer. The processed message data with the additional data and/or thereserved space can be reloaded into the ring buffer or another memory.Afterwards, the temporary buffer can be de-allocated.

It should be understood that the operations illustrated in Tables 1-5are for illustrative purposes and not meant to be limiting upon theinvention.

Alternative Embodiments

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described. For instance, while the flowdiagrams show a particular order of operations performed by certainembodiments of the invention, it should be understood that such order isexemplary (e.g., alternative embodiments may perform the operations in adifferent order, combine certain operations, overlap certain operations,etc.). For example, with reference to FIG. 5B, block 526 is performedbefore blocks 523 and/or 525 in an alternative embodiments of theinvention. With reference to FIG. 6B, block 623 is performed beforeblocks 619, 621, and/or 622 in an alternative embodiments of theinvention.

Thus, the method and apparatus of the invention can be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The description is thus to be regarded as illustrative insteadof limiting on the invention.

1. A method in a network device comprising: determining if a resourcelocator identifier (RLI) in a response indicates an appropriate requestgoverning resource access protocol, wherein the appropriate requestgoverning resource access protocol is the resource access protocol togovern a request for a resource indicated by the RLI, wherein theappropriate request governing resource access protocol is determinedfrom a configuration file; and rewriting the RLI to indicate theappropriate request governing resource access protocol if the RLI doesnot indicate the appropriate request governing resource access protocol;and preventing a client that receives the response from relying on thecontent length indicated in the response by effectively removing acontent length field in the response, wherein effectively removing thecontent length field comprises modifying the content length field in theresponse to be unrecognizable.
 2. The method of claim 1 wherein theappropriate request governing resource access protocol is a secureresource access protocol.
 3. The method of claim 1 wherein theappropriate request governing resource access protocol is a non-secureresource access protocol.
 4. A method in a network device comprising:modifying a response with a resource locator identifier (RLI) toindicate a first resource access protocol if the RLI indicates a secondresource access protocol and the network device has been configured toinsure that a request for a resource indicated by the RLI is inaccordance with the first resource access protocol; effectively removinga content length field in the response, wherein effectively removing thecontent length field comprises modifying the content length field in theresponse to be unrecognizable; and transmitting the modified response toa client.
 5. The method of claim 4 wherein the first resource accessprotocol is a secure resource access protocol and the second resourceaccess protocol is a non-secure resource access protocol.
 6. The methodof claim 4 further comprising disabling persistent connection andchunked transfer encoding.
 7. The method of claim 4 further comprising:preserving persistent connection and chunked transfer encoding featuresavailable to the client; and disabling chunked transfer encodingfeatures for a resource host transmitting the response.
 8. A method in anetwork security device comprising: receiving a response with a resourcelocator identifier (RLI) that indicates a first resource accessprotocol; determining that the first resource access protocol should notgovern a request for a resource indicated by the RLI; rewriting the RLIto indicate a second resource access protocol that should govern therequest; encapsulating a set of one or more fragments of the responsewith transport layer information; effectively removing a content lengthfield in the response, wherein effectively removing the content lengthfield comprises modifying the content length field in the response to beunrecognizable; and transmitting the encapsulated set of fragments to aclient.
 9. The method of claim 8 wherein rewriting the RLI includesadding port information to the RLI.
 10. The method of claim 8 whereinthe first resource access protocol is a secure resource access protocoland the second resource access protocol is a non-secure resource accessprotocol.
 11. The method of claim 8 further comprising disablingpersistent connection and chunked transfer encoding.
 12. The method ofclaim 8 further comprising: preserving persistent connection and chunkedtransfer encoding features available to the client; and disablingchunked transfer encoding features for a resource host transmitting theresponse.
 13. A machine-readable medium that provides instructions,executable by a set of one or more processors to cause said set ofprocessors to perform operations comprising: receiving a resourceresponse message; scanning the resource response message for a set ofone or more resource locator identifiers and determining if each of theset of resource locator identifiers indicates a resource access protocolthat should govern a request for their indicated resource; rewritingthose of the set of resource locator identifiers that are determined tonot indicate the resource access protocol that should govern a requestfor their indicated resource to indicate an appropriate requestgoverning resource access protocol; and effectively removing a contentlength indicated in the resource response message, wherein effectivelyremoving the content length field comprises modifying the content lengthfield in the resource response message to be unrecognizable.
 14. Themachine-readable medium of claim 13 further comprising transmitting theresponse without scanning and rewriting if the content type of theresponse is not text.
 15. The machine-readable medium of claim 13further comprising transmitting the response without scanning andrewriting if the header of the response does not include a contentencoding field.
 16. The machine-readable medium of claim 13 whereinrewriting the set of resource locator identifiers comprises including acorresponding port.
 17. The machine-readable medium of claim 13 whereindetermining comprises comparing the resource host identifier of each ofthe set of resource locator identifiers against a configuration filethat designates appropriate request governing resource access protocolsfor resource hosts.
 18. A machine-readable medium that providesinstructions, executable by a set of one or more processors to causesaid set of processors to perform operations comprising: determining ifa resource locator identifier (RLI) in a response indicates anappropriate request governing resource access protocol, wherein theappropriate request governing resource access protocol is the resourceaccess protocol to govern a request for a resource indicated by the RLI,wherein the appropriate request governing resource access protocol isdetermined from a configuration file; and rewriting the RLI to indicatethe appropriate request governing resource access protocol if the RLIdoes not indicate the appropriate request governing resource accessprotocol; and preventing a client that receives the response fromrelying on the content length indicated in the response by effectivelyremoving a content length field in the response, wherein effectivelyremoving the content length field comprises modifying the content lengthfield in the response to be unrecognizable.
 19. The machine-readablemedium of claim 18 wherein the appropriate request governing resourceaccess protocol is a secure resource access protocol.
 20. Themachine-readable medium of claim 18 wherein the appropriate requestgoverning resource access protocol is a non-secure resource accessprotocol.
 21. A machine-readable medium that provides instructions,executable by a set of one or more processors to cause said set ofprocessors to perform operations comprising: modifying a response with aresource locator identifier (RLI) to indicate a first resource accessprotocol if the RLI indicates a second resource access protocol and thenetwork device has been configured to insure that a request for aresource indicated by the RLI is in accordance with the first resourceaccess protocol; effectively removing the content length field in theresponse, wherein effectively removing the content length fieldcomprises modifying the content length field in the response to beunrecognizable; and transmitting the modified response to a client. 22.The machine-readable medium of claim 21 wherein the first resourceaccess protocol is a secure resource access protocol and the secondresource access protocol is a non-secure resource access protocol. 23.The machine-readable medium of claim 21 further comprising disablingpersistent connection and chunked transfer encoding.
 24. Themachine-readable medium of claim 21 further comprising: preservingpersistent connection and chunked transfer encoding features availableto the client; and disabling chunked transfer encoding features for aresource host transmitting the response.